CN102305607A - Calibration method for measuring thickness of oxidation layer on inner wall of boiler tube by ultrasonic wave - Google Patents

Abstract

Translated fromChinese

本发明公开了超声波无损探伤技术领域中的一种超声波测量锅炉管内壁氧化层厚度的校准方法。该发明的校准方法基于氧化层的双层结构，分层标定超声波在其中的传播速度，进而校准氧化层厚度。该方法具有坚实的科学依据，能够显著提高锅炉管内壁氧化层厚度超声波测量的精确度。

The invention discloses a calibration method for ultrasonically measuring the thickness of an oxide layer on the inner wall of a boiler tube in the technical field of ultrasonic nondestructive flaw detection. The calibration method of the invention is based on the double-layer structure of the oxide layer, and the propagation speed of the ultrasonic wave in it is calibrated layer by layer, and then the thickness of the oxide layer is calibrated. The method has a solid scientific basis and can significantly improve the accuracy of ultrasonic measurement of the thickness of the oxide layer on the inner wall of the boiler tube.

Description

The calibration steps of ultrasonic measurement boiler tube inner wall oxide layer thickness

Technical field

The invention belongs to the ultrasonic flaw detection technical field, relate in particular to a kind of calibration steps of ultrasonic measurement boiler tube inner wall oxide layer thickness.

Background technology

Measure boiler tube inner wall oxide layer thickness, adopt the high-frequency ultrasonic thickness measuring system, form, can differentiate transmitting of oxide layer/metallic matrix interface, thereby measure oxidated layer thickness by the high frequency probe and the ultrasonic pulse generation/receiver of high-frequency narrow-pulse.

If acquiescence ultrasound wave velocity of propagation in oxide layer equates that with velocity of propagation in the tube wall metal oxidated layer thickness can directly be read from defectoscope, this also is a method commonly used now.Also have the people that the velocity of propagation of ultrasound wave in oxide layer demarcated, after severing through pipeline, thickness is measured in microscopic examination, demarcates ultrasound wave in the oxide layer velocity of propagation.But demarcate ultrasonic velocity through different-thickness oxide layer, when finding that oxide layer is thin, the velocity of sound is very little, and the velocity of sound increases with oxidated layer thickness, about 2800 meter per seconds of difference that the velocity of sound of demarcation is minimum and maximum, and measurement causes very mistake to oxidated layer thickness.This scaling method is not distinguished the sandwich construction of oxide layer; Ultrasound wave is different in the velocity of propagation of different layers; Above-mentioned phenomenon will appear in timing signal, and therefore above-mentioned demarcation calibration steps fundamentally can't adapt to the accurate measurement of the oxidated layer thickness of sandwich construction.

Boiler tube inner wall oxide layer thickness can calculate tube wall equivalence running temperature, and extremely important to the life-span management of boiler tube, therefore a kind of internal oxidation layer of boiler tube accurately thickness measuring calibration steps is that Practical significance is arranged very much.

Summary of the invention

To the bigger deficiency of mentioning in the above-mentioned background technology of existing boiler tube inner wall oxide layer thickness measuring result error, the present invention proposes a kind of calibration steps of ultrasonic measurement boiler tube inner wall oxide layer thickness.Technical scheme of the present invention is that the calibration steps of ultrasonic measurement boiler tube inner wall oxide layer thickness is characterized in that this method may further comprise the steps:

Step 1: defectoscope, high frequency probe and computer are constituted ultrasonic measurement system; High frequency probe is fitted in the boiler tube outer wall; Adjustment defectoscope form and gain; Observe inner wall oxide layer ultrasonoscopy; When obtaining clearly tube wall metal and internal oxidation layer interface echo, internal oxidation layer and external oxidation bed interface echo and external oxidation layer and air interface echo, preserve image and also be sent to computer;

Step 2: on the image that step 1 obtains, obtain the measured value of internal oxidation layer and external oxidation layer thickness respectively, boiler tube inner wall oxide layer thickness is calibrated through the different velocity of propagation of ultrasound wave in tube wall metal, internal oxidation layer and external oxidation layer.

The model of said defectoscope is Karl Deustch ECHOGRAPH 1090 DAC.

The frequency of said high frequency probe is 15 megahertzes.

The computing formula of said oxidated layer thickness is:

${\mathrm{\&delta;}}^{\&prime;}={\mathrm{\&delta;}}_{\mathrm{inner}}\&times;\frac{C_{L1}}{{\mathrm{<figure-callout\; label="C\; L"\; filenames="HDA0000063402490000011.png,HDA0000063402490000021.png"\; state="\{\{state\}\}">C</figure-callout>}}_L}+{\mathrm{\&delta;}}_{\mathrm{outer}}\&times;\frac{C_{L2}}{{\mathrm{<figure-callout\; label="C\; L"\; filenames="HDA0000063402490000011.png,HDA0000063402490000021.png"\; state="\{\{state\}\}">C</figure-callout>}}_L}$

Wherein:

δ ' is the oxidated layer thickness after calibrating;

δ_InnerThe internal oxidation layer thickness of directly measuring for ultra-sonic defect detector;

δ_OuterThe external oxidation layer thickness of directly measuring for ultra-sonic defect detector;

C_L0Be the velocity of propagation of ultrasound wave in the tube wall metal;

C_L1Be the velocity of propagation of ultrasound wave in internal oxidation layer;

C_L2Be the ultrasound wave velocity of propagation of oxide layer outside.

Calibration steps of the present invention is based on the double-decker of oxide layer, and ultrasound wave velocity of propagation is therein demarcated in layering, and then the calibration oxidated layer thickness.This method has solid scientific basis, can significantly improve the degree of accuracy of boiler tube inner wall oxide layer thickness ultrasonic measurement.

Description of drawings

Fig. 1 is a boiler tube inner wall oxide layer thickness ultrasonic measurement system;

Fig. 2 propagates synoptic diagram for ultrasound wave in the inner wall oxide layer;

Fig. 3 is the echo of ultrasound wave at the inner wall oxide Es-region propagations.

Embodiment

Below in conjunction with accompanying drawing, preferred embodiment is elaborated.Should be emphasized that following explanation only is exemplary, rather than in order to limit scope of the present invention and application thereof.

Through to 9-12% ferrochrome martensite steel (comprise P91, P92, P122, the HT9) research of oxidizing process in water vapor and supercritical water environment finds that the inner wall oxide layer has typical double-decker, i.e. Zhi Mi four oxidations, two ferrochrome FeCr₂O₄The tri-iron tetroxide Fe of internal oxidation layer and rough porous₃O₄The external oxidation layer.Because the elastic constant of this double-layer structure material is different with density, ultrasound wave velocity of propagation therein is different.

Ultrasound wave compressional wave velocity of propagation in solid can be expressed as:

$C_L=\sqrt{\frac{\mathrm{\&lambda;}+2u}{\mathrm{\&rho;}}}---\left(1\right)$

Wherein:

C_LBe the ultrasonic compressional velocity of wave propagation;

λ and u are Lame's constant;

ρ is a density.

Table 1 is listed four oxidations, two ferrochrome FeCr₂O₄With tri-iron tetroxide Fe₃O₄Lame's constant, density, and ultrasound wave velocity of propagation therein.

Table 1 FeCr₂O₄And Fe₃O₄Elasticity coefficient and ultrasonic propagation velocity

Use Karl Deustch ECHOGRAPH 1090 DAC defectoscopes, the high frequency probe of 15 megahertzes and a computer constitute ultrasound wave boiler inner wall oxidated layer thickness measuring system, as shown in Figure 1.Because tube wall metal, four oxidations, two ferrochrome FeCr₂O₄Internal oxidation layer and tri-iron tetroxide Fe₃O₄The acoustic impedance of external oxidation layer is different, all reflection wave can be arranged at tube metal/internal oxidation layer interface and internal oxidation layer/place, external oxidation bed interface.Ultrasound wave is propagated synoptic diagram and is seen Fig. 2 in oxide layer.The adjustment ultra-sonic defect detector can obtain hyperacoustic echo, sees Fig. 3.Can clearly obtain reflection wave one through figure, reflection wave two and reflection wave three, the distance between reflection wave one and the reflection wave two is an internal oxidation layer thickness, the distance between reflection wave two and the reflection wave three is the external oxidation layer thickness.Therefore just can according to different ultrasonic propagation velocities, calibrate respectively through measuring the thickness of internal oxidation layer thickness and external oxidation layer respectively, addition obtains whole oxidated layer thickness then.The oxidated layer thickness calibration equation is following:

${\mathrm{\&delta;}}^{\&prime;}={\mathrm{\&delta;}}_{\mathrm{inner}}\&times;\frac{C_{L1}}{{\mathrm{<figure-callout\; label="C\; L"\; filenames="HDA0000063402490000011.png,HDA0000063402490000021.png"\; state="\{\{state\}\}">C</figure-callout>}}_L}+{\mathrm{\&delta;}}_{\mathrm{outer}}\&times;\frac{C_{L2}}{C_{L0}}---\left(2\right)$

Wherein:

δ ' is the oxidated layer thickness after calibrating;

δ_InnerThe internal oxidation layer thickness of directly measuring for ultra-sonic defect detector;

δ_OuterThe external oxidation layer thickness of directly measuring for ultra-sonic defect detector;

C_L0Be the velocity of propagation of ultrasound wave in the tube wall metal;

C_L1Be the velocity of propagation of ultrasound wave in internal oxidation layer;

C_L2Be the ultrasound wave velocity of propagation of oxide layer outside.

C_L1And C_L2Value see table 1, adoptformula 2 to realize the calibration calculations of ultrasonic measurement boiler tube inner wall oxide layer thicknesses.

Step of the present invention is:

1, use Karl Deustch ECHOGRAPH 1090 DAC defectoscopes, the high frequency probe of 15MHz and a notebook constitute boiler tube inner wall oxide layer thickness ultrasonic measurement system.Set the velocity of propagation C of ultrasound wave in the tube wall metal_L0(user can set according to practical application);

2, the boiler tube outside surface is handled totally, high frequency probe is fitted tightly at the boiler tube outer wall, measure boiler tube internal oxidation layer thickness.Move the form of defectoscope and adjust the gain of defectoscope, when observing clearly the ultrasonic echo image, computer is preserved and be sent to this image;

3, the ultrasonic echo image is measured the measured value δ of the distance acquisition internal oxidation layer thickness between reflection wave one and the reflection wave two as shown in Figure 3_Inner, measure between reflection wave two and the reflection wave three apart from the measured value δ that obtains the external oxidation layer thickness_Outer, revise according toformula 2 then, obtain revised oxidated layer thickness δ ';

Table 2 is two instances of the boiler tube internal oxidation layer thickness that adopts this calibration steps and measure, with scanning electron microscopic observation to the oxide layer actual (real) thickness compare, error is less, compares ultra-sonic defect detector and directly measures thickness and precision and obviously improve.This invention calibration steps is based on the double-decker of oxide layer, and ultrasound wave velocity of propagation is therein demarcated in layering, and then the calibration oxidated layer thickness.This method has solid scientific basis, can significantly improve the degree of accuracy of boiler tube inner wall oxide layer thickness ultrasonic measurement.

Table 2 boiler tube inner wall oxide layer thickness ultrasonic measurement calibration, the μ m of unit

The above; Only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and any technician who is familiar with the present technique field is in the technical scope that the present invention discloses; The variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of claim.

Claims (4)

1. the calibration steps of ultrasonic measurement boiler tube inner wall oxide layer thickness is characterized in that this method may further comprise the steps:

Step 1: defectoscope, high frequency probe and computer are constituted ultrasonic measurement system; High frequency probe is fitted in the boiler tube outer wall; Adjustment defectoscope form and gain; Observe inner wall oxide layer ultrasonoscopy; When obtaining clearly tube wall metal and internal oxidation layer interface echo, internal oxidation layer and external oxidation bed interface echo and external oxidation layer and air interface echo, preserve image and also be sent to computer;

Step 2: on the image that step 1 obtains, obtain the measured value of internal oxidation layer and external oxidation layer thickness respectively, boiler tube inner wall oxide layer thickness is calibrated through the different velocity of propagation of ultrasound wave in tube wall metal, internal oxidation layer and external oxidation layer.

2. according to the calibration steps of the said ultrasonic measurement boiler tube of claim 1 inner wall oxide layer thickness, the model that it is characterized in that said defectoscope is Karl Deustch ECHOGRAPH 1090 DAC.

3. according to the calibration steps of the said ultrasonic measurement boiler tube of claim 1 inner wall oxide layer thickness, the frequency that it is characterized in that said high frequency probe is 15 megahertzes.

4. according to the calibration steps of the said ultrasonic measurement boiler tube of claim 1 inner wall oxide layer thickness, it is characterized in that the computing formula of said oxidated layer thickness is:

${\mathrm{\&delta;}}^{\&prime;}={\mathrm{\&delta;}}_{\mathrm{inner}}\&times;\frac{C_{L1}}{C_{L0}}+{\mathrm{\&delta;}}_{\mathrm{outer}}\&times;\frac{C_{L2}}{C_{L0}}$

Wherein:

δ ' is the oxidated layer thickness after calibrating;

δ_InnerThe internal oxidation layer thickness of directly measuring for ultra-sonic defect detector;

δ_OuterThe external oxidation layer thickness of directly measuring for ultra-sonic defect detector;

C_L0Be the velocity of propagation of ultrasound wave in the tube wall metal;

C_L1Be the velocity of propagation of ultrasound wave in internal oxidation layer;

C_L2Be the ultrasound wave velocity of propagation of oxide layer outside.

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